Wheat planted in corn stubble at risk for head scab

More corn acres brought on by high corn prices in recent years could tempt winter wheat growers to plant the crop into corn stubble, but a Purdue Extension pathologist says the practice puts wheat at risk for head scab development.

Head scab, or Fusariam head blight, is caused by the fungus Gibberella zeae, also known as Fusarium graminearum, which is harbored in corn residue. In corn, the fungus causes ear and stalk rots, and in wheat can lead to yield loss and reduced grain quality. The disease also produces a mycotoxin called deoxynivalenol, also called DON or vomitoxin, which is toxic to humans and livestock.

“There is a yearly concern for wheat planted into corn stubble because the fungus that causes head scab also causes Gibberella ear rot in corn,” Kiersten Wise said. “Even though this was a year when we didn’t have a lot of Gibberella ear rot, there were some reports of it, and fields with wheat following corn would be at risk in those situations.”

Gibberella zeae can overwinter in corn residue and produce spores in the spring. High humidity and frequent rainfall in the spring can help disperse the spores to wheat plants. Wheat is most susceptible to infection during growth stages between flowering and dough.

Wise said winter wheat growers could lower the risk by planting the crop in fields that produced non-host crops, such as soybeans.

“Our initial recommendation is to not plant wheat after corn, but we know that’s a practice that a lot of growers are going to do,” she said. “So what we would recommend is that they select a variety that has resistance to Fusarium head blight, or scab. Next spring they need to pay attention to the weather as wheat starts to flower and decide if they need to apply a fungicide to manage scab.

“No single disease-management tactic will provide adequate control of this disease, especially if environmental conditions favor disease development.”

More information about head scab in wheat is available in Purdue Extension’s publication, “Diseases of Wheat: Fusarium Head Blight (Head Scab)” at http://www.extension.purdue.edu/extmedia/BP/BP-33-W.pdf . The publication, authored by Wise and Purdue Extension plant pathologist Charles Woloshuk, includes information about identification, mycotoxin tolerance levels, safe grain handling, disease management and more.